In theory it should be possible, but of course the risk is that when you attempt it it will lead to a cascading set of issues which will end up in a complete re-chassis project anyway.
A 1975 car is highly likely to have significant rot in the body frame, especially the rocker panels under the doors, and any attempt to lift the body from the chassis is going to result in the frame breaking and panels tearing.
If it was me and I had an 18 month wait before I could get the car into a decent space for a re-chassis project I'd be spending the time getting the bits assembled and planning the sequence of work. I was planning on doing a re-chassis project on mine some years ago but quickly realised it was going to be a huge job that I had neither the time nor space to do properly so I ended up getting Kevin Vernon to do it for me.
